Prior to the Apostolic Constitution Universi Dominici Gregis — promulgated on February 22, 1996 that changed the rules governing papal conclaves — participants were forced to sleep in the Apostolic Palace on rented cots, usually borrowed from seminaries in Rome. After participants were literally sealed under lock and key in the Apostolic Palace, the electors would live in makeshift rooms built throughout the palace, including within hallways and offices. The rooms, assigned to each Cardinal by lot, would often be constructed by nothing more than a sheet hanging on a rope. Sturdier walls would not be available because of the cost and because they would damage the Palace walls. In addition to the rented cots, each room would be equipped with a Crucifix and kneeler, a desk and one or two chairs. The Cardinals would have to share common bathrooms, often with ten Cardinals assigned to each. The situation would especially be difficult as the Cardinals tend to be elderly gentlemen.

Pope John Paul II, after himself participating in two Conclaves, decided to make the process more comfortable and less strenuous on the elderly Cardinals and commissioned the construction of Domus Sanctæ Marthæ.

As with previous practice, the Cardinals would be assigned their rooms by lot. Cardinals' rankings would have no effect on which room they would receive. Cardinal Ratzinger, in the 2005 Conclave, was assigned to a simple room even though he was the Cardinal Dean and one of the longest-serving in the College; after he had been elected Pope, he was invited to transfer to the fancier Patriarchal Suite. The new pope, known for his humility and only having become Pope a few hours earlier, is said to have been astonished at the invitation to a superior room.

During a Conclave, all radios, television sets and telephones would be disconnected, as per regulations which call for the Cardinals to be secluded from the outside world to prevent any undue influence on their voting.

According to Professor Mary Ann Glendon in an interview with EWTN, the Domus Sanctae Marthae does not resemble a five-star hotel as the Western media often represents it to be; rather, it was designed according to standards of monastic simplicity.